1. Field of the Art
This invention relates to the field of breast lesion localization and biopsy, and more particularly to an apparatus for localizing a breast lesion by scintigraphy in three dimensions and in real-time.
2. Description of the Prior Art
The occurrence of breast cancer is a leading cause of death for women. Women are advised to conduct breast self examination for palapable lumps or bumps on a monthly basis, and after the age of 40, to undergo mammography at least on a bi-annual basis in order to detect nonpalapable lesions. Presently, special roentgenography, or x-ray techniques for photographically studying the mammary gland, or breast, are utilized to locate lesion with greater success than with self-examination, particularly with small lesion located deep in the breast. However, one major problem with traditional x-ray mammography is that there is little selectivity in what is imaged. In addition to malignant carcinoma tumors, generally harmless calcifications, proliferative changes, fibroadenomas, and fibrocystic changes show up. Indeed, while x-ray mammography has a high sensitivity of 85-90%, it currently predicts malignancy in only about 20-30% of mammography suspicious lesions. Since the radiologist has great difficulty in distinguishing malignancy from harmless lesions, biopsy and tissue cultures must be carried out to determine if the lesion is malignant. In fact, in around 80% of the cases where biopsies are performed, the lesions prove not to be malignant.
In order to effectively conduct the x-ray mammography, the patient's breast being imaged must be compressed with great and uncomfortable force to squeeze the breast to a thickness of about three to four and a half centimeters so that the x-rays can adequately penetrate the breast and develop the film lying behind the breast. This process must be conducted in two separate planes. First, the breast is compressed in a horizontal plane, so a cranial and caudal projection can be taken. The next projection taken is a mediolateral oblique view, wherein the breast is compressed in a vertical plane. These two initial views taken together make up the screening mammography.
The radiologist will then read the x-ray negatives to determine if there are any lesions or other signs of lesions in the breast. If the radiologist sees any suspicious lesions, then "special views" are taken. Actually, the same views as in a screening are carried out, except that the compressed breast is slightly displaced from the film plate to effect magnification of any lesions in the breast. If the radiologist finds a suspicious lesion, a biopsy needle will be inserted into the lesion site of the anesthetized breast.
After the needle is placed in the breast, another x-ray image will be taken, to determine how close the tip of the needle is to the lesion. Several adjustments of the needle and several x-ray photographs may be required to position the needle at the lesion site. Once the biopsy needle is positioned near the lesion site, a hooked guide wire will be pushed through the biopsy needle and hooked onto the lesion. The guide wire provides the surgeon with a traceable path to the lesion. The surgeon will then remove either a sample of the lesion (i.e. by aspiration biopsy), or the entire lesion in surgical biopsy procedure, and the tissue removed will be examined by the oncologist. This process is time consuming, painful, physically scaring, and expensive. The patient will then wait a few agonizing days to learn of the test results. Again, since by x-ray mammography the radiologist cannot readily distinguish between malignant and non-malignant lesions, when suspicious lesions are located, biopsy are required. Since statistically 80% of all lesions are non-malignant, present x-ray mammography technique results in many unnecessary biopsies.
Several approaches have been explored to better locate the position of the lesion in a patient's breast by x-ray mammography. U.S. Pat. No. 5,209,232 to Levene uses computerized device to accurately detect the position of lesions in the breast, and to position the biopsy needle. U.S. Pat. No. 5,289,520 to Pellegrino et al. and U.S. Pat. No. 5,078,192 to Siczek et al. provide automated breast lesion locator imaging and biopsy systems.
U.S. Pat. No. 5,056,523 to Hotchikiss, Jr. et al. discloses a device and method for precisely positioning the tip of a probe into a breast lesion. Radiopaque markers are used to identify the position of the lesion relative to a fenestrate compression grid. To determine the depth of the lesion in the breast, a certain amount of trial and error is required. A similar system is provided by the method and apparatus of U.S. Pat. No. 4,875,478 to Chen. The Chen apparatus used a radiolucent compression support plate with calibration marks, with a movable biopsy needle support guide, so that the biopsy needle can be positioned with its tip in the lesion. Notwithstanding the improvements provided by these x-ray mammography devices, major problems remain in that many unnecessary biopsies will still be to be performed.
Another new, experimental method utilizes contrast material-enhanced magnetic resonance (MR) mammography, and is disclosed in "MR Mammographic Localization, Work in Progress", by K. Hussman et al. Radiology, Vol. 189, No. 3, pp. 915-917. By this method, after MR resonance enhancing agents are injected into the patient's bloodstream, her breast being examined is placed in an open box with two fenestrated perpendicular side walls. The position of the lesion in the X, Y and Z coordinates is noted, and the precise position of the biopsy needle will then be sought to be located. Since the magnetic resonance apparatus is quite narrow to enter, the needle must be inserted after the patient's breast is imaged. To avoid the breast shifting in the box, the breast is best temporary adhered to the box with medical grade adhesive. The technique of the Hussman et al. device, is highly uncomfortable, cumbersome, and expensive, and makes this approach disfavored.
Recently, the use of Technetium-99m Sestamibi (sold under the name Cardiolite.RTM., by the DuPont Merck Pharmaceutical Co., Billerica, Mass.) has been explored to accurately detect the presence of carcinoma of the breast. See "Review of Imaging Techniques for the Diagnosis of Breast Cancer, a New Role of Prone Scintimammography using Technetium-99m Sestamibi", by I. Khalkhali, I. Mena, and L. Diggles, European Journal of Nuclear Medicine, Vol. 21, No. 4, April 1994, pp. 357-362, and "Prone Scintimammography in Patients with Suspicion of Carcinoma of the Breast", by I. Khalkhali, I. Mena, E. Jouanne, L. Diggles, R. Venegas, J. Block, K. Alle, and S. Klein, Journal of American College of Surgeons, May 1994, Vol. 178, pp.491-97.
Scintimammography is the method to detect the presence of malignant tumors by radioactive substances which selectively accumulate in the malignant tumors, or carcinomas.
By utilizing the method of scintimammography with Technetium-99m Sestamibi, the inventors have reported a negative predictive value for the presence of carcinoma of 97.5%, a sensitivity of 96%, and a specificity of 85%. More importantly, by the method of scintimammography using Technetium-99m Sestamibi, malignant lesions as small as 2.about.3 mm or smaller can be diagnosed.
However, there has not been as of yet a method and apparatus for accurately localizing carcinomas of the breast by real-time scintimammography. There accordingly remains a need for a scintigraphy guided stereotaxic localization apparatus and method for carcinomas of the breast.